• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.529-547
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• 2011

This paper presents the global-local finite cover method (GL-FCM) that is capable of analyzing structures involving local heterogeneities and propagating cracks. The suggested method is composed of two techniques. One of them is the FCM, which is one of the PU-based generalized finite element methods, for the analysis of local cohesive crack growth. The mechanical behavior evaluated in local heterogeneous structures by the FCM is transferred to the overall (global) structure by the so-called mortar method. The other is a method of mesh superposition for hierarchical modeling, which enables us to evaluate the average stiffness by the analysis of local heterogeneous structures not subjected to crack propagation. Several numerical experiments are conducted to validate the accuracy of the proposed method. The capability and applicability of the proposed method is demonstrated in an illustrative numerical example, in which we predict the mechanical deterioration of a reinforced concrete (RC) structure, whose local regions are subjected to propagating cracks induced by reinforcement corrosion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.1001-1004
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• 2000

As tools for machining precision components, end mills and ball end mills are widely used. For the end mills have longer cylindrical shape comparing diameter, liable to deflect and induce deterioration of surface roughness. Tool geometry parameters and cutting process have complex relations with each other. So, It is hard to determine hew to select optimal tool geometry. So, to improve the stiffness, relationship between cutting process and tool geometry must be studied. In this study, relations between grinding wheel geometry, setting condition and tool geometry are revealed. For the purpose of studying relations between each parameter, the equivalent diameter of tool has been calculated assuming tool as a simple beam. By the various cutting simulations and experiments, tool geometry and cutting process has been studied.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.6
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• pp.49-57
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• 2003

This method surely needs a hole that causes local strength and stiffness deterioration of the structure because of stress intensity. In this work, three dimensional stress analysis of pin-loaded joint for quasi-isotropic composite laminates was performed using commercial finite element software. Stress distribution was calculated near the edge of the pin-leaded hole and effects of the stacking sequence on the delamination were investigated. Also, the delamination strength of the composite laminates was predicted using the Ye-delamination failure criterion and compared with the experimental results. finally, newly modified failure criterion has been suggested owing to the consideration of effects of interlaminar normal stress on the delamination strength.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.101-108
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• 2001

In the previous study, an improved QRD (QR Decomposition)-ILS(Iterative Least-Squares) method is proposed to estimate the structural parameters at the element level using response data alone without using any information of excitation measurements for the assessment of local damages and deterioration in complex and large structural systems. But for a complex and large structural system, where response measurement at every dynamic degree of freedom(DDOF) is not possible, the absence of some observation points of responses and its effect on the proposed SI method must be studied In the paper, a QRD-ILS technique that utilizes the known intact stiffness information estimated based on the visual inspection, field measurements and/or NDT tests is proposed to identify local damages of fracture critical members using measured responses only at limited DDOFs. A numerical example is used to illustrate the application of this technique. The results indicate that the proposed SI technique is very simple but efficient, since no input information are required with only limited observations.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.85-92
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• 1998

Most of tall apartment buildings constructed in our county are wall-type R/C structures composed of hear walls and slabs. It is necessary to evaluate of hysteretic properties of shear walls in wall-type R/C structures which resist lateral loads as well as axial loads. In this study, first to evaluate the wall's hysteretic behavior nonlinear analyses with IDARC 4.0 are performed for eight specimens subjected to horizontal load reversals. As a result of nonlinear analyses of specimens we can obtain three parameters which determined the hysteretic parameters such as stiffness degrading, strength deterioration and inching behavior respectively. With this three parameters, strength and deformation capacity of 5, 10, 20-story shear wall of apartment building is estimated from the results of push-over analysis.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1097-1102
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• 2009

In a railway vehicle, corrugated steel panel is widely used for the floor panel because of its high bending stiffness and light weight. However, this panel shows lower sound insulation performance than that of the plate with the same weight. Especially, in a particular frequency band, transmission loss (TL) rapidly decreases and it results in the deterioration of TL of the overall floor panel. This study identifies that the remarkable drop in TL is caused from the local resonance of the periodic corrugated structure. This study shows that the frequency band of the TL drop can be controlled by the proper design of the corrugated structure. In addition, improvement effect of TL by attaching foam and glass wool is estimated by experiment. The purpose of the study is to provide the practical information for the improvement of the sound insulation performance of the corrugated steel.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.793-799
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• 2004

In track a third weakness point is joint part, turnout part, curve part. One of them joint part of rail have been known to the most weak point by loosen of joint bar and fish bolt due to impulse and vibration by wheel contact at times. In addition happen to deformation and failure at end of rail, failure and miniature of ballast gravel. Finally impact between wheel and rail become origin cause of a welded rail, noise and vibration. riding condition deterioration, besides track failure. In the present domestic, Thermite and Gas pressure weldings have been used to continuous welded rail(CWR), however stiffness and confidence in quality is lower than Flash butt welding method. FRW have the excellent capacity, however have a shortcoming large scale of machine and power equipment. Therefore we will introduce Mobile Flash Butt Welder can weld in track.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.8-15
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• 2006

In this report Smart UAV structural analysis of the aft fuselage is presented. Aft fuselage needs to have enough strength and stiffness considering loads of the Vertical and Horizontal Stabilizer together. It has a big hole for the purpose of engine exhaust duct on its side body. In addition, much attention is needed in high temperature region due to material strength deterioration.

• Computational Structural Engineering
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• v.4 no.1
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• pp.133-142
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• 1991

A mathematical hysteretic model has been developed to analytically reproduce the experimental hysteretic behavior of reinforced concrete members. This mode[2, 3] can simulate the nonlinear response of reinforced concrete members with sufficient accuacy, which are characterized by following important hysteretic behaviors: stiffness degradation, strength deterioration and shear effect. In order to illustrate the capabilities of the proposed mathematical model, numerical examples are presented with the reproduction of experimental hysteretic behavior of RC members and frames.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.513-518
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• 2001

This research has been performed to estimate the hunting motion hysteresis of railway passenger cars. An old and a new car with almost same structure are chosen as analysis models. To solve effectively a set of simultaneous equations of motion strongly coupled with creep relations, shooting algorithm in which the nonlinear relations are regarded as a two-point boundary value problem is adopted. The bifurcation theory is applied to the dynamic analysis to distinguish differences between linear and nonlinear critical speeds by variation of parameters. It is found that there are some factors and their operation area to make nonlinear critical speed respond to them more sensitivity than linear critical speed. Full-scale roller rig tests are carried out for the validation of the numerical results. Finally, it is concluded that the wear of wheel profile and the stiffness discontinuities of wheelset suspension caused by deterioration have to be considered in the analysis to predict hysteresis of critical speed precisely.